This paper provides an update of our previous scaling relations (Genzel et al. 2015) between galaxy integrated molecular gas masses, stellar masses and star formation rates, in the framework of the star formation main-sequence (MS), with the main goal to test for possible systematic effects. For this purpose our new study combines three independent methods of determining molecular gas masses from CO line fluxes, far-infrared dust spectral energy distributions, and ~1mm dust photometry, in a large sample of 1444 star forming galaxies (SFGs) between z=0 and 4. The sample covers the stellar mass range log(M*/M)=9.0-11.8, and star formation rates relative to that on the MS, δMS=SFR/SFR(MS), from 10 -1.3 to 10 2.2 . Our most important finding is that all data sets, despite the different techniques and analysis methods used, follow the same scaling trends, once method-to-method zero point offsets are minimized and uncertainties are properly taken into account. The molecular gas depletion time tdepl, defined as the ratio of molecular gas mass to star formation rate, scales as (1+z) -0.6 × (δMS) -0.44 , and is only weakly dependent on stellar mass. The ratio of molecular-to-stellar mass μgas depends on (1+z) 2.5 × (δMS) 0.52 × (M*) -0.36 , which tracks the evolution of the specific star formation rate. The redshift dependence of μgas requires a curvature term, as may the mass-dependences of tdepl and μgas. We find no or only weak correlations of tdepl and μgas with optical size R or surface density once one removes the above scalings, but we caution that optical sizes may not be appropriate for the high gas and dust columns at high-z.

We combine molecular gas masses inferred from CO emission in 500 star forming galaxies (SFGs) between z=0 and 3, from the IRAM-COLDGASS, PHIBSS1/2 and other surveys, with gas masses derived from Herschel far-IR dust measurements in 512 galaxy stacks over the same stellar mass/redshift range. We constrain the scaling relations of molecular gas depletion time scale (t depl ) and gas to stellar mass ratio (M molgas /M * ) of SFGs near the star formation 'main-sequence' with redshift, specific star formation rate (sSFR) and stellar mass (M * ). The CO-and dust-based scaling relations agree remarkably well. This suggests that the CO  H 2 mass conversion factor varies little within ±0.6dex of the main sequence (sSFR(ms,z,M * )), and less than 0.3dex throughout this redshift range. This study builds on and strengthens the results of earlier work. We find that t depl scales as (1+z) -0.3  (sSFR/sSFR(ms,z,M * )) -0.5 , with little dependence on M * . The resulting steep redshift dependence of M molgas /M *  (1+z) 3 mirrors that of the sSFR and probably reflects the gas supply rate. The decreasing gas fractions at high M * are driven by the flattening of the SFR-M * relation. Throughout the redshift range probed a larger sSFR at constant M * is due to a combination of an increasing gas fraction and a decreasing depletion time scale. As a result galaxy integrated samples of the M molgas -SFR rate relation exhibit a super-linear slope, which increases with the range of sSFR. With these new relations it is now possible to determine M molgas with an accuracy of ±0.1dex in relative terms, and ±0.2dex including systematic uncertainties.

We report on the detailed analysis of a gravitationally-lensed Y-band dropout, A2744 YD4, selected from deep Hubble Space Telescope imaging in the Frontier Field cluster Abell 2744. Band 7 observations with the Atacama Large Millimeter Array (ALMA) indicate the proximate detection of a significant 1mm continuum flux suggesting the presence of dust for a star-forming galaxy with a photometric redshift of z 8. Deep X-SHOOTER spectra confirms the high redshift identity of A2744 YD4 via the detection of Lyman α emission at a redshift z=8.38. The association with the ALMA detection is confirmed by the presence of [OIII] 88µm emission at the same redshift. Although both emission features are only significant at the 4 σ level, we argue their joint detection and the positional coincidence with a high redshift dropout in the HST images confirms the physical association. Analysis of the available photometric data and the modest gravitational magnification (µ 2) indicates A2744 YD4 has a stellar mass of ∼ 2×10 9 M , a star formation rate of ∼ 20 M /yr and a dust mass of ∼6×10 6 M . We discuss the implications of the formation of such a dust mass only 200 Myr after the onset of cosmic reionisation.

We discuss the efficiency of stellar gravity torques as a mechanism to account for the feeding of the central engines of four low luminosity Active Galactic Nuclei (AGN): NGC 4321 (HII nucleus/LINER), NGC 4826 (HII nucleus/LINER), NGC 4579 (LINER 1.9/Seyfert 1.9) and NGC 6951 (Seyfert 2). These galaxies have been observed as part of the NUclei of GAlaxies-(NUGA) CO project, aimed at the study of AGN fueling mechanisms. Our calculations allow us to derive the characteristic time-scales for gas flows and discuss whether torques from the stellar potentials are efficient enough to drain the gas angular momentum in the inner 1 kpc of these galaxies. The stellar potentials are derived using high-resolution near infrared (NIR) images and the averaged effective torques on the gas are estimated using the high-resolution (∼0.5 -2 ) CO maps of the galaxies. Results indicate paradoxically that feeding should be thwarted close to the AGNs: in the four cases analyzed, gravity torques are mostly positive inside r ∼ 200 pc, resulting in no inflow on these scales. As a possible solution for the paradox, we speculate that the agent responsible for driving inflow to still smaller radii is transient and thus presently absent in the stellar potential. Alternatively, the gravity torque barrier associated with the Inner Lindblad Resonance of the bars in these galaxies could be overcome by other mechanisms that become competitive in due time against gravity torques. In particular, we estimate on a case-by-case basis the efficiency of viscosity versus gravity torques to drive AGN fueling. We find that viscosity can counteract moderate-to-low gravity torques on the gas if it acts on a nuclear ring of high gas surface density contrast and ∼a few 100 pc size. We propose an evolutionary scenario in which gravity torques and viscosity act in concert to produce recurrent episodes of activity during the typical lifetime of any galaxy. In this scenario the recurrence of activity in galaxies is indirectly related to that of the bar instabilities although the active phases are not necessarily coincident with the maximum strength of a single bar episode. The general implications of these results for the current understanding of fueling of low-luminosity AGN are discussed.

We present new deep ALMA and HST/WFC3 observations of MASOSA and VR7, two luminous Lyα emitters (LAEs) at z = 6.5, for which the UV continuum level differ by a factor four. No IR dust continuum emission is detected in either, indicating little amounts of obscured star formation and/or high dust temperatures. MASOSA, with a UV luminosity M 1500 = −20.9, compact size and very high Lyα EW 0 ≈ 145Å, is undetected in [Cii] to a limit of L [CII] < 2.2 × 10 7 L implying a metallicity Z 0.07Z . Intriguingly, our HST data indicates a red UV slope β = −1.1 ± 0.7, at odds with the low dust content. VR7, which is a bright (M 1500 = −22.4) galaxy with moderate color (β = −1.4 ± 0.3) and Lyα EW 0 = 34Å, is clearly detected in [Cii] emission (S/N=15). VR7's rest-frame UV morphology can be described by two components separated by ≈ 1.5 kpc and is globally more compact than the [Cii] emission. The global [Cii]-UV ratio indicates Z ≈ 0.2Z , but there are large variations in the UV-[Cii] ratio on kpc scales. We also identify diffuse, possibly outflowing, [Cii]-emitting gas at ≈ 100 km s −1 with respect to the peak. VR7 appears assembling its components at a slightly more evolved stage than other luminous LAEs, with outflows already shaping its direct environment at z ∼ 7. Our results further indicate that the global [Cii]-UV relation steepens at SFR < 30 M yr −1 , naturally explaining why the [Cii]-UV ratio is anti-correlated with Lyα EW in many, but not all, observed LAEs.

During our Herschel Lensing Survey (HLS) of massive galaxy clusters, we have discovered an exceptionally bright source behind the z = 0.22 cluster Abell 773, which appears to be a strongly lensed submillimeter galaxy (SMG) at z = 5.2429. This source is unusual compared to most other lensed sources discovered by Herschel so far, because of its higher submm flux (∼200 mJy at 500 μm) and its high redshift. The dominant lens is a foreground z = 0.63 galaxy, not the cluster itself. The source has a far-infrared (FIR) luminosity of L FIR = 1.1 × 10 14 /μ L , where μ is the magnification factor, likely ∼11. We report here the redshift identification through CO lines with the IRAM-30 m, and the analysis of the gas excitation, based on CO(7-6), CO(6-5), CO(5-4) detected at IRAM and the CO(2-1) at the EVLA. All lines decompose into a wide and strong red component, and a narrower and weaker blue component, 540 km s −1 apart. Assuming the ultraluminous galaxy (ULIRG) CO-to-H 2 conversion ratio, the H 2 mass is 5.8 × 10 11 /μ M , of which one third is in a cool component. From the C I( 3 P 2 − 3 P 1 ) line we derive a C I/H 2 number abundance of 6 × 10 −5 similar to that in other ULIRGs. The H 2 O p (2, 0, 2−1, 1, 1) line is strong only in the red velocity component, with an intensity ratio I(H 2 O)/I(CO) ∼ 0.5, suggesting a strong local FIR radiation field, possibly from an active nucleus (AGN) component. We detect the [NII]205 μm line for the first time at high-z. It shows comparable blue and red components, with a strikingly broad blue one, suggesting strong ionized gas flows.

We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [C II] 158 m m line-emission at high spatial resolution matched to the HST/WFC3 imaging. CR7 is a luminous Lyα emitting galaxy at z=6.6 that consists of three separated UV-continuum components. . The observed ISM structure of CR7 indicates that we are likely witnessing the build up of a central galaxy in the early universe through complex accretion of satellites.

Context. Determining the dust properties and UV attenuation of distant star-forming galaxies is of great interest for our understanding of galaxy formation and cosmic star formation in the early Universe. However, few direct measurements exist so far. Aims. To shed new light on these questions, we have targeted two recently discovered Lyman-break galaxies (LBGs) at z ≈ 6.8 and z = 7.508 to search for dust continuum and [C ii] λ158 μm line emission.Methods. The strongly lensed z ≈ 6.8 LBG A1703-zD1 behind the galaxy cluster Abell 1703 and the spectroscopically confirmed z = 7.508 LBG z8-GND-5296 in the GOODS-N field were observed with the Plateau de Bure Interferometer (PdBI) at 1.2 mm. These observations were combined with those of three z > 6.5 Lyα emitters (HCM6A, Himiko, and IOK-1), for which deep measurements were recently obtained with the PdBI and ALMA.Results. [C ii] is undetected in both galaxies, providing a deep upper limit of L [C II] < 2.8 × 10 7 L for A1703-zD1, comparable to the nondetections of Himiko and IOK-1 with ALMA. Dust continuum emission from A1703-zD1 and z8-GND-5296 is not detected with an rms of 0.12 and 0.16 mJy/beam. From these nondetections and earlier multiwavelength observations we derive upper limits on their IR luminosity and star formation rate, dust mass, and UV attenuation. Thanks to strong gravitational lensing, the achieved limit for A1703-zD1 is similar to those achieved with ALMA, probing below the luminous infrared galaxy (LIRG) regime (L IR < 8.1×1010 L ) and very low dust masses (M d < 1.6 × 10 7 M ). We find that all five galaxies are compatible with the Calzetti IRX-β relation, their UV attenuation is compatible with several indirect estimates from other methods (the UV slope, extrapolation of the attenuation measured from the IR/UV ratio at lower redshift, and spectral energy distribution fits), and the dust-to-stellar mass ratio is compatible with that of galaxies from z = 0 to 3. From their stellar mass, the high-z galaxies studied here have an attenuation below the one expected from the mean relation of low-redshift (z < ∼ 1.5) galaxies. Conclusions. More and deeper (sub-)mm data are clearly needed to directly determine the UV attenuation and dust content of the dominant population of high-z star-forming galaxies and to establish their dependence on stellar mass, redshift, and other properties more firmly.